Boric Acid as a Coupling Agent for Preparation of Phenolic Resin Containing Boron and Silicon with Enhanced Char Yield

Abstract

In this study, an innovative, facile, and low‐cost method is developed to prepare phenolic resin (PR) containing boron and silicon (BSiPR). BSiPR is synthesized by a solvent‐free, one‐pot method using boric acid as the coupling agent instead of silane, and methyltriethoxysilane as the silicon source. The results show that boron and silicon elements are introduced into PR via BOC and BOSi structures. The char yield of the resulting resin at 800 °C is improved to 76%. The reasons for higher char yield are investigated. The formation of BOC can reduce the content of phenolic hydroxyl, which helps to decrease the weight loss. B2O3 is also formed at 400 °C, and it can prevent the release of carbon oxides. Moreover, thermally stable BOSi and SiO structures remain stable during the pyrolysis. In addition, the mechanical and ablative properties of fiber‐reinforced composites are also enhanced.

Synthesis and Properties of a Silicon‐Containing Arylacetylene Resin with 2,6‐Diphenoxypyridine Unit

“…As shown in Figure , the water uptake gradually increases with time. Finally, water uptake of cured PSPPY resin is approaching 0.8 % at room temperature, which is much lower than that of phenolic resin . This illustrates that the cured PSPPY resin has potential practicability in humid environment.…”

A bifunctional modifier endowing epoxy resin with outstanding flame retardancy and high impact strength

“…The residue char of the thermosets was enhanced from 13.4% to 18.5% with the increasing of DPPO‐TES contents, higher than that of EP (8.3%), illustrating that DPPO‐TES possessed excellent charring ability for EP materials. According to our previous work, 34,37 the introduction of Si to the EP matrix could significantly increase its thermal stability and SiO structures were stable during the whole pyrolysis process, which was beneficial to reduce weight loss.…”

“…It could be seen that the characteristic peak of oxirane at 831 cm −1 decreased successively and the absorption bond of OH at 3500 cm −1 increased obviously with the increasing of DPPO‐TES content in the modified EP, indicating the epoxy groups were consumed via the ring‐open reaction with SiOH, which was hydrolyzed from DPPO‐TES. In addition, the absorption peaks at 1000–1100 cm −1 were assigned to SiOSi structure, which was due to the condensation of SiOH 34 . Therefore, as shown in Scheme 1, there were two main reactions in the DPPO‐TES/EP system.…”

Strong Effect of Process Parameters on the Properties of Boron-Containing Phenolic Resins with High Char Yield

“…The characteristic absorption peaks around 1237 cm −1 for common PR and 1222 cm −1 for B-containing PR correspond to the C-O bond of phenolic hydroxyl, and the stretching vibration peak of C-O bond for residual phenol hydroxyl is weakened visibly. The characteristic absorption peak of the C-O bond for benzyl hydroxyl is located at about 1100 cm −1 [27,28]. Notably, the B-containing PR exhibits a new strong absorption peak at about 1455 cm −1 , which is attributed to the characteristic peak of the B-O bond compared with that of common PR, indicating successful incorporation of the B element by the current simple method [13,27].…”